In a pot heat the oil over medium high heat. Stir in the onions, celery and potatoes and cook for about 5 minutes. Pour in the chicken stock and water and bring to a boil. Reduce heat and simmer the soup for 20 minutes or until the potatoes are tender.
Season the soup with salt and pepper. Stir in the escarole and cook for 2-3 minutes. Serve immediately with crusty bread and grated parmesan